Thanos Network Upgrade Preserves GPU Mining

Ethereum Classic activated the Thanos network upgrade at block 11,700,000 on November 28, 2020, implementing ECIP-1099 to modify the mining algorithm's DAG growth schedule.

## The DAG Size Problem

The Ethash mining algorithm requires miners to store a DAG (Directed Acyclic Graph) in GPU memory. The DAG grows approximately 8 MB every 30,000-block epoch (~5 days). By late 2020, the DAG was approaching the 4 GB memory limit of consumer GPUs like the GTX 1050 Ti and RX 570/580, which would force these miners offline.

## ECIP-1099: Epoch Doubling

Thanos doubled the DAG epoch from 30,000 to 60,000 blocks, halving the DAG growth rate. This extended the viability of 4GB GPU mining by approximately three additional years.

## Etchash Algorithm

With the epoch length change, ETC's mining algorithm is now called Etchash to distinguish it from Ethereum's Ethash. The algorithms are identical in all other respects — the only difference is the epoch duration parameter. Existing mining software required only minor configuration updates.

## Mining Decentralization

The decision preserved mining accessibility for operators running consumer-grade hardware, preventing centralization toward ASIC operators and large GPU farms with 8GB+ cards. This aligns with ETC's commitment to censorship resistance through distributed mining.

## Client Requirements

- Core-Geth v1.11.22 or later
- Hyperledger Besu with ETC Thanos support